Automated brewing machines such as coffee and tea makers typically have a brewing water reservoir wherein water is heated by a heating element inside of or in contact with the reservoir. Heated water is then transferred from the reservoir, typically by thermal expansion or displacement, to a brewing chamber or basket which holds a brewing material such as coffee grounds or tea leaves, through which the heated water flows to produce a brewed beverage which drains into a carafe or pitcher positioned underneath the brewing chamber.
The rate of flow of heated water through the brewing material in the brewing chamber directly affects the content and taste of the brewed beverage. For example, a relatively fast rate of flow of hot water through coffee grounds in the brewing chamber will result in relatively diluted coffee with relatively less flavor and caffeine, than is produced by a slower rate of flow. And to correctly brew decaffeinated coffee grounds, a relatively slower rate of flow should be used in order to achieve a taste comparable to "regular" or caffeinated coffee which is brewed with a relatively faster rate of flow. In a displacement style brewing machine, the rate at which the heated water flows into the brewing chamber is primarily a function of the rate at which water is introduced to the reservoir, the size of the conduit or passage between the reservoir and the brewing chamber, and the size of holes in a water distributor or showerhead over the brewing chamber. The rate of flow through the brewing chamber is also a function of the size of the drainage hole at bottom of the basket. These dimensions are typically fixed, leaving no practical means for adjusting the rate of flow for brewing different types of beverages.
Some attempts have been made to enable adjustment of flow rate by, for example, providing an adaptable, interchangeable showerhead with different hole sizes; but this approach is cumbersome, labor-intensive, and dependent upon availability of the part or parts to be interchanged. Reduced-opening showerheads may not provide optimal water distribution over the brewing material in the brewing chamber. Furthermore, showerhead flow rate adjustment does not address the rate of flow into the reservoir.
Another operational difficulty associated with automated brewing machines is that the brewing cycle, i.e., the heating of water in the reservoir and flow through and out of the brewing chamber, may commence immediately upon introduction of additional water into the reservoir. This is especially the case in the well-known displacement type brewing machine, wherein a charge of hot brewing water sits in wait in the reservoir to be displaced into the brewing basket immediately upon introduction of additional water from a separate filling chamber connected to the reservoir. This necessitates that a carafe or pitcher be positioned underneath the brewing chamber as water is added to the filling chamber. Thus a second pitcher is needed to measure and pour water into the reservoir. The requirement of a separate filling pitcher is burdensome, especially in the context of machines designed primarily for domestic use.
U.S. Pat. No. 5,251,541 describes a displacement type brewing machine wherein a stopper directly engages a fill port between a fill basin and a heating reservoir when water is being added to the fill basin. The stopper is connected to one end of a pivotal arm. The other end of the pivotal arm may be contacted by a cam on a shaft which depends from a lid selectively covering an opening to the fill basin. When the lid is in the closed position, the cam on the shaft contacts the other end of the arm to thereby pivot that arm and lift the stopper out of engagement with the fill port, allowing water to drain through the fill port into the reservoir. When the lid is opened by swinging it to the side, the cam is moved out of contact with the arm, allowing the arm to pivot in the opposite direction so that the stopper directly engages and covers the fill port. While this structure accomplishes suspension of the brewing cycle until the lid on the fill tray is closed, it does not allow any variable rate flow control mechanism to be incorporated into or associated with the fill port, as the stopper must be positioned directly over the fill port.